Hi All, The particular radar is on the coast road in Norfolk, between Bacton [gas terminal] and Sherringham.
I have passed this in a number of cars over the years - none of which have shown the slightest of effects. However, cars have more electronics which probably have smaller feature sizes in line with the general advancement of electronics. In the article, a "golf ball" was mentioned. This is a radome, a RF transparent cover, over the radar - thereby preventing me from seeing whether the radar antenna has recently been changed. As vehicles become more complex in terms of the electronics, it becomes more difficult to test them. In addition, human safety limits are time averaged whereas many electronic circuits will respond to a peak RF field. Assuming that the previous public exposure limit was complied with - 10mW/cm^2 or 200V/m, then the peak field could be in the order of 6600V/m at the roadside. I would expect that vehicles are not certified to that kind of level :-( Regards Tim From: [email protected] [mailto:[email protected]]On Behalf Of Robert A. Macy Sent: 26 February 2006 00:52 To: John Woodgate Cc: [email protected] Subject: Re: Interesting UK EMC problem *** WARNING *** This mail has originated outside your organization, either from an external partner or the Global Internet. Keep this in mind if you answer this message. Thank you for the URL. Looks like a conscientious, responsible approach. They admit their limits are higher than those proposed in some unconvincing literature. I believe the US limits are based upon some type of OSHA approach, just limiting to below the threshold of pain. It is my recollection that the limits of Sweden's MPRII rules were originally based upon someone finding a correlation between incidence of cancer and the presence of electrical distribution lines, after studying historical statistics. It is my understanding that the author calculated the magnetic field exposure and concluded that 2mG was the "magic" level. Below that level few cases, above that level, significant incidences of cancer. There's a huge trail of info somewhere on the net regarding all the claims flying back and forth. Basically, the conclusion was 'there is no evidence'. Most of the papers came down to posturing between "Yes it does." or "No, it doesn't." I personally believe that the effect between magnetic field and biology do not follow our intuitive attitude that 'more is worse'. The biological interaction may only appear in "ranges" of exposure and therefore be contrary to our intuitive attitude of a "threshold of exposure". Instead of the damaging effects showing after exceeding some level/magnitude, they appear after exposure to certain "ranges" of exposure. In other words, a little won't hurt you, a lot won't hurt you, but watch out for the range between blank and blank. Such an unusual relationship between magnitude and observable effects would make post analyses of epidemiological data nearly impossible. Indeed, post analyses of historical data show no conclusive evidence of any relationship between exposure to magnetic fields and ill health. It is true that the calcium ion is susceptible to magnetic fields and the calcium ion is used in the cell's mitosis processes. It is also true that the calcium ion will only precess at certain frequencies in certain levels of biasing magnetic field. The AC main's single frequency can only precess/perturb the calcim ion in a specific range of biasing field. Else, no precession. Such a relationship between frequency and biasing fields could explain why a range of exposure is more important than a threshold of exposure. I have also seen papers purporting the "transient" nature of the exposure as being more important. The authors' premise is that transitions between levels of exposure is more damaging than a steady exposure. Along that line... Here in San Jose there was a "sick" building near by us. [As I recall] the county government building had 15 cases of one of the rarest forms of cancerous brain tumors. The number of cases in this one building was more than the total number of cases in all of the US over the history of accumulating data. A widow of one of the unfortunate 'victims' appeared on Geraldo Rivera's TV show, discussing her lawsuit for ?? regarding her husband's recent death. Very tragic. The building had two almost identical wings. Yet, oddly all the cases happened in the west wing, none in the east wing. Both wings were built at the same time, of the same materials, share same facilities - heating, electrical distributions, etc. An extensive study was performed looking for differences between the two wings, but the report found nothing significantly different between the two wings. The researchers were fairly thorough, even measuring the energy of the radar scans from San Jose's nearby airport. I talked with the California epidemiologist as the investigation was nearing completion. She was really frustrated that nothing was found. According to her, this form of cancer is prevalent, but very slow growing in people. Onset starts around 40 or 50 and can take 30 to 40 years to develop to the state of causing symptoms. She said, you're more likely to die of old age before any symptoms appear. She said she didn't feel the "unknown" cause was creating cancer, merely accellerating it. She felt something accellerated the cancer, causing its growth spurt and its earlier appearance. But again, nothing was found during the official investigation. As with all urban areas, the area around San Jose has been changing during our building boom. Guadalupe corridor, where the building is located, was rebuilt and modernized, which meant that the Utility's 115KV high tension tower lines were removed and placed underground. These towers held two sets of a-b-c phasing with doubled cabling each to share current loads. Over 1000 Amps flowed with spacing more than 15 feet. That produces a lot of field directly between the towers at the maximum cable droop. Historically, many employees who worked in the west wing of the sick building, and only those employees, would take advantage of the closeness of the open area under those towers and "illegally" park underneath the towers and run across the roadway to go to work - very short distance compared to the distance to the supplied parking structures. The practise of conveniently parking under the towers lasted for a significant number of years, before the modernization removed the towers, widened the road into a significant highway, *and* required all employees to park in the proper parking structures, north of the building. Since reconstruction, no new cases. It was my contention that somehow exposure to the transient fields, concentrated as you get in and out of your car, was accellerating the incidences of cancer growth. I tried, unsuccessfully, to get access and funding to investigate the characteristics of the exposure and search for a correlation between the 'victims' and their parking habits. Hopefully, exposure to magnetic fields won't go the route of exposure to asbestos and uranium ore went. So, maybe judicious avoidance is still the best strategy. > [sneep] sneep?! Manuel from Fawlty Towers? I'll gladly discuss the NDE Instrumentation off-group. Thank you again for the "heads up" on ICNIRP's efforts. - Robert - On Sat, 25 Feb 2006 09:09:20 +0000 John Woodgate <[email protected]> wrote: > In message <[email protected]>, dated Fri, 24 > Feb 2006, Robert A. Macy <[email protected]> writes > >Don't know what ICNIRP Guidelines are, > > http://www.icnirp.de/documents/emfgdl.pdf > > >but as I recall the > >old Swedish MPRII rules were on the order of 200nT over > the > >band of 5Hz to 2000Hz and 20nT over the band of 2KHz to > >400KHz. [From memory, so numbers could be off] > > Those are very small fields. The ICNIRP numbers are > higher, and are still regarded as 'very conservative'. > There are FCC limits in USA, which differ from the > ICNIRP. > > > [sneep] > > > > > >PS the meter was my own invention and had sensitivity > of > >1V per microTesla with flat response from 5Hz to over 1 > >MHz. I was amazed how easy it was for the earth's 50uT > to > >get into that bandwidth with very small movements of the > >meter. > > > >For an NDE application to replace noisy Hall Effect and > GMR > >sensors, I extended the range of the meter down to 0.001 > >Hz. The circuits took all morning long to "turn on". > > Hated that delay. But with a 2 minute time constant > and > >0.1% accuracy, what are you going to do? > > NDE? I'd be interested in more details of your meter, if > possible. > > > >40 year SHORT course? hmm....all is relative, right? > > Vita brevis... > > > > > >What is the reasoning behind the ICNIRP Guidelines at > >around 1/4 earth's field? > > The URL above gives a lot of rationale. > > >Who is requiring the guidelines > >be met? > > > There is a new specific European EMF Directive about > exposure of workers to ElectroMagnetic Fields, but there > is something that affects ALMOST EVERY electrical and > electronic product in Europe. The control of 'radiation' > to safe limits is an Essential requirement of the Low > Voltage Directive. When it was written, people probably > had only ionizing radiation (X-rays for TV tubes) in > mind, but it is now held that non-ionizing radiation is > included, and every product that has not had its magnetic > (and/or electric) field emissions assessed has not > satisfied the requirements of the Directive. There is a > lot of activity in CENELEC TC106X and IEC TC106 on the > preparation of Generic and other general standards, but > progress is difficult because many people involved are > relatively new to standards work and don't know the best > way to do things. > > This work isn't widely known about. Just like for EMC, > product committees should be writing EMF standards > (giving detailed operating conditions for, and methods > of, measurement) for their products, but only the > household appliance committee has yet done this. > -- > OOO - Own Opinions Only. Try www.jmwa.demon.co.uk and > www.isce.org.uk > 2006 is YMMVI- Your mileage may vary immoderately. > > John Woodgate > > - > > This message is from the IEEE Product Safety Engineering > Society > emc-pstc discussion list. Website: > http://www.ieee-pses.org/ > > To post a message to the list, send your e-mail to > [email protected] > > Instructions: > http://listserv.ieee.org/request/user-guide.html > > List rules: http://www.ieee-pses.org/listrules.html > > For help, send mail to the list administrators: > > Scott Douglas [email protected] > Mike Cantwell [email protected] > > For policy questions, send mail to: > > Jim Bacher: [email protected] > David Heald: [email protected] > > All emc-pstc postings are archived and searchable on the > web at: > > http://www.ieeecommunities.org/emc-pstc - This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. 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